Method of filtering signals for a controller of a turbo compressor

摘要

Method of filtering both noisy and fluctuating input signals for a controller which is used for controlling the operation of a turbo compressor comprises obtaining an input signal from the operating device and before delivering an input signal to the controller correcting these signals through a filter whose time constant is small in one direction for example a decreasing or increasing signal amplitude directed toward the pumping limit of the operating device whose time constant is great in the other direction increasing or decreasing signal amplitude particularly away from the limit being controlled. Advantageously the filtered signal is compared with an unfiltered signal and the time constant of the filter is set as the function of the magnitude and the sign of the difference between the filtered and unfiltered signal. In addition the time constant may be reduced to a permanently pre-selected value possibly to zero when a switching threshold in a limit stages unilaterally exceeded. To be going below a switching threshold the time constant may be reset to the original time constant either immediately or after the constant is offset by hysteresis threshold.